Cable robots

Cable-driven parallel robots (also called cable robots, cable-suspended robots or wire-driven robots) are a type of <a href="/facts/Parallel_manipulator/kxkX2Cyg">parallel manipulators</a> in which flexible <a href="/facts/Wire_rope/9z4b9SYB">cables</a> are used as <a href="/facts/Actuator/mF9qVJJR">actuators</a>. One end of each cable is reeled around a <a href="/facts/Rotor_(electric)/TJegVHtc">rotor</a> twisted by a <a href="/facts/Engine/p0m7aXaW">motor</a>, and the other end is connected to the <a href="/facts/Robot_end_effector/XsSbw5wa">end-effector</a>. One famous example of cable robots is <a href="/facts/Skycam/vbUbDtIK">Skycam</a> which is used to move a suspended <a href="/facts/Camera/j4uqsfJQ">camera</a> in <a href="/facts/Stadium/AFCDDj1f">stadiums</a>. Cables are much lighter than rigid linkages of a serial or <a href="/facts/Parallel_manipulator/kxkX2Cyg">parallel robot</a>, and very long cables can be used without making the mechanism massive. As a result, the end-effector of a cable robot can achieve high <a href="/facts/Acceleration/UVDmjYvR">accelerations</a> and <a href="/facts/Velocity/Q3o1LVDe">velocities</a> and work in a very large workspace (e.g. a stadium). Numerous <a href="/facts/Engineering/RFVg8H3I">engineering</a> articles have studied the <a href="/facts/Kinematics/o7mSyeJA">kinematics</a> and <a href="/facts/Dynamics_(mechanics)/JLk81H71">dynamics</a> of cable robots (e.g. see In <a href="/facts/The_International_Journal_of_Robotics_Research/pH4L4n4s">The International Journal of Robotics Research</a> 27.9 (2008): 1007–1026. for an enhanced of the concept). Dynamic analysis of cable robots is not the same as that of other parallel robots because cables can only pull an object but they cannot push. Therefore, the manipulator is able to perform a task only if the <a href="/facts/Force/533Q1uzq">force</a> in all cables are non-negative. Accordingly, the workspace of cable robots is defined as a region in space where the end-effector is able to <a href="/facts/Exertion/goEFAQXC">exert</a> the required wrench (force and moment vectors) to the surroundings while all cables are in <a href="/facts/Tension_(physics)/waNGYp3a">tension</a> (non-negative forces). Many research works have focused on workspace analysis and optimization of cable robots. Workspace and controllability of cable robots can be enhanced by adding cables to structure of the robot. Consequently, <a href="/facts/Redundancy_(engineering)/odqzTmIo">redundancy</a> plays a key role in design of cable robots.

However, workspace analysis and obtaining positive tension in cables of a <a href="/facts/Redundant_binary_representation/R6kcefzo">redundant</a> cable robot can be complicated. In general, for a redundant robot, infinite solution may exist, but for a redundant cable robot a solution is acceptable only if all the elements of <a href="/facts/Tension_(physics)/waNGYp3a">tension</a> vector are non-negative. Finding such a solution can be challenging, especially if the end-effector is working along a <a href="/facts/Trajectory/STNN33FK">trajectory</a> and a continuous and smooth distribution of tensions is desired in cables. In literature, several methods have been presented to solve such problems a <a href="/facts/Computational_methods_for_free_surface_flow/nB9jBkMR">computational method</a> is introduced based on <a href="/facts/Particle_swarm_optimization/QYo2YaP7">Particle Swarm Optimization</a> method to find continuous smooth solutions along a trajectory for a general redundant cable robot).
In addition to parallel cable robots, cables have been used as <a href="/facts/Actuator/mF9qVJJR">actuators</a> in serial robots as well. By employing cables as actuators a mechanism can be designed much smaller and lighter (e.g. a human-like finger mechanism actuated by cables is presented in ).

Cable robots open-in-new

Cable robots